/**
 * Copyright (c) 2014, Timothy Stack
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * * Redistributions of source code must retain the above copyright notice, this
 * list of conditions and the following disclaimer.
 * * Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 * * Neither the name of Timothy Stack nor the names of its contributors
 * may be used to endorse or promote products derived from this software
 * without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ''AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * @file json-extension-functions.cc
 */

#include "config.h"

#include <string.h>

#include <string>

#include "sqlite3.h"

#include "yajlpp/yajlpp.hh"
#include "yajlpp/json_op.hh"
#include "mapbox/variant.hpp"
#include "vtab_module.hh"

#include "yajl/api/yajl_gen.h"
#include "sqlite-extension-func.hh"

using namespace std;
using namespace mapbox;

#define JSON_SUBTYPE  74    /* Ascii for "J" */

class sql_json_op : public json_op {
public:
    sql_json_op(json_ptr &ptr) : json_op(ptr), sjo_type(-1), sjo_int(0) { };

    int sjo_type;
    string sjo_str;
    int sjo_int;
};

static void null_or_default(sqlite3_context *context, int argc, sqlite3_value **argv)
{
    if (argc > 2) {
        sqlite3_result_value(context, argv[2]);
    }
    else {
        sqlite3_result_null(context);
    }
}

struct contains_userdata {
    util::variant<const char *, sqlite3_int64, bool> cu_match_value{false};
    bool cu_result{false};
};

static int contains_string(void *ctx, const unsigned char *str, size_t len)
{
    auto &cu = *((contains_userdata *) ctx);

    if (strncmp((const char *) str, cu.cu_match_value.get<const char *>(), len) == 0) {
        cu.cu_result = true;
    }

    return 1;
}

static int contains_integer(void *ctx, long long value)
{
    auto &cu = *((contains_userdata *) ctx);

    if (cu.cu_match_value.get<sqlite3_int64>() == value) {
        cu.cu_result = true;
    }

    return 1;
}

static bool json_contains(const char *json_in, sqlite3_value *value)
{
    auto_mem<yajl_handle_t> handle(yajl_free);
    yajl_callbacks cb;
    contains_userdata cu;

    memset(&cb, 0, sizeof(cb));
    handle = yajl_alloc(&cb, nullptr, &cu);

    switch (sqlite3_value_type(value)) {
        case SQLITE3_TEXT:
            cb.yajl_string = contains_string;
            cu.cu_match_value = (const char *) sqlite3_value_text(value);
            break;
        case SQLITE_INTEGER:
            cb.yajl_integer = contains_integer;
            cu.cu_match_value = sqlite3_value_int64(value);
            break;
    }

    if (yajl_parse(handle.in(), (const unsigned char *) json_in, strlen(json_in)) != yajl_status_ok ||
        yajl_complete_parse(handle.in()) != yajl_status_ok) {
        throw yajlpp_error(handle.in(), json_in, strlen(json_in));
    }

    return cu.cu_result;
}

static int gen_handle_null(void *ctx)
{
    sql_json_op *sjo = (sql_json_op *)ctx;
    yajl_gen gen = (yajl_gen)sjo->jo_ptr_data;

    if (sjo->jo_ptr.jp_state == json_ptr::MS_DONE) {
        sjo->sjo_type = SQLITE_NULL;
    }
    else {
        sjo->jo_ptr_error_code = yajl_gen_null(gen);
    }

    return sjo->jo_ptr_error_code == yajl_gen_status_ok;
}

static int gen_handle_boolean(void *ctx, int boolVal)
{
    sql_json_op *sjo = (sql_json_op *)ctx;
    yajl_gen gen = (yajl_gen)sjo->jo_ptr_data;

    if (sjo->jo_ptr.jp_state == json_ptr::MS_DONE) {
        sjo->sjo_type = SQLITE_INTEGER;
        sjo->sjo_int = boolVal;
    }
    else {
        sjo->jo_ptr_error_code = yajl_gen_bool(gen, boolVal);
    }

    return sjo->jo_ptr_error_code == yajl_gen_status_ok;
}

static int gen_handle_string(void *ctx, const unsigned char * stringVal, size_t len)
{
    sql_json_op *sjo = (sql_json_op *)ctx;
    yajl_gen gen = (yajl_gen)sjo->jo_ptr_data;

    if (sjo->jo_ptr.jp_state == json_ptr::MS_DONE) {
        sjo->sjo_type = SQLITE3_TEXT;
        sjo->sjo_str = string((char *)stringVal, len);
    }
    else {
        sjo->jo_ptr_error_code = yajl_gen_string(gen, stringVal, len);
    }

    return sjo->jo_ptr_error_code == yajl_gen_status_ok;
}

static void sql_jget(sqlite3_context *context,
                     int argc, sqlite3_value **argv)
{
    if (argc < 2) {
        sqlite3_result_error(context, "expecting JSON value and pointer", -1);
        return;
    }

    if (sqlite3_value_type(argv[0]) == SQLITE_NULL) {
        null_or_default(context, argc, argv);
        return;
    }

    const char *json_in = (const char *)sqlite3_value_text(argv[0]);

    if (sqlite3_value_type(argv[1]) == SQLITE_NULL) {
        sqlite3_result_text(context, json_in, -1, SQLITE_TRANSIENT);
        return;
    }

    const char *ptr_in = (const char *)sqlite3_value_text(argv[1]);
    json_ptr jp(ptr_in);
    sql_json_op jo(jp);
    auto_mem<yajl_handle_t> handle(yajl_free);
    const unsigned char *err;
    yajlpp_gen gen;

    yajl_gen_config(gen, yajl_gen_beautify, false);

    jo.jo_ptr_callbacks = json_op::gen_callbacks;
    jo.jo_ptr_callbacks.yajl_null = gen_handle_null;
    jo.jo_ptr_callbacks.yajl_boolean = gen_handle_boolean;
    jo.jo_ptr_callbacks.yajl_string = gen_handle_string;
    jo.jo_ptr_data = gen.get_handle();

    handle.reset(yajl_alloc(&json_op::ptr_callbacks, nullptr, &jo));
    switch (yajl_parse(handle.in(), (const unsigned char *)json_in, strlen(json_in))) {
    case yajl_status_error:
        err = yajl_get_error(handle.in(), 0, (const unsigned char *)json_in, strlen(json_in));
        sqlite3_result_error(context, (const char *)err, -1);
        return;
    case yajl_status_client_canceled:
        if (jo.jo_ptr.jp_state == json_ptr::MS_ERR_INVALID_ESCAPE) {
            sqlite3_result_error(context, jo.jo_ptr.error_msg().c_str(), -1);
        }
        else {
            null_or_default(context, argc, argv);
        }
        return;
    default:
        break;
    }

    switch (yajl_complete_parse(handle.in())) {
    case yajl_status_error:
        err = yajl_get_error(handle.in(), 0, (const unsigned char *)json_in, strlen(json_in));
        sqlite3_result_error(context, (const char *)err, -1);
        return;
    case yajl_status_client_canceled:
        if (jo.jo_ptr.jp_state == json_ptr::MS_ERR_INVALID_ESCAPE) {
            sqlite3_result_error(context, jo.jo_ptr.error_msg().c_str(), -1);
        }
        else {
            null_or_default(context, argc, argv);
        }
        return;
    default:
        break;
    }

    switch (jo.sjo_type) {
    case SQLITE3_TEXT:
        sqlite3_result_text(context, jo.sjo_str.c_str(), jo.sjo_str.size(), SQLITE_TRANSIENT);
        return;
    case SQLITE_NULL:
        sqlite3_result_null(context);
        return;
    case SQLITE_INTEGER:
        sqlite3_result_int(context, jo.sjo_int);
        return;
    }

    string_fragment result = gen.to_string_fragment();

    if (result.empty()) {
        null_or_default(context, argc, argv);
        return;
    }

    sqlite3_result_text(context, result.data(), result.length(), SQLITE_TRANSIENT);
}

struct concat_context {
    concat_context(yajl_gen gen_handle)
        : cc_gen_handle(gen_handle) {
    }

    yajl_gen cc_gen_handle;
    int cc_depth{0};
};

static int concat_gen_null(void *ctx)
{
    auto cc = static_cast<concat_context *>(ctx);

    if (cc->cc_depth > 0) {
        return yajl_gen_null(cc->cc_gen_handle) == yajl_gen_status_ok;
    }

    return 1;
}

static int concat_gen_boolean(void *ctx, int val)
{
    auto cc = static_cast<concat_context *>(ctx);

    return yajl_gen_bool(cc->cc_gen_handle, val) == yajl_gen_status_ok;
}

static int concat_gen_number(void *ctx, const char *val, size_t len)
{
    auto cc = static_cast<concat_context *>(ctx);

    return yajl_gen_number(cc->cc_gen_handle, val, len) == yajl_gen_status_ok;
}

static int concat_gen_string(void *ctx, const unsigned char *val, size_t len)
{
    auto cc = static_cast<concat_context *>(ctx);

    return yajl_gen_string(cc->cc_gen_handle, val, len) == yajl_gen_status_ok;
}

static int concat_gen_start_map(void *ctx)
{
    auto cc = static_cast<concat_context *>(ctx);

    cc->cc_depth += 1;
    return yajl_gen_map_open(cc->cc_gen_handle) == yajl_gen_status_ok;
}

static int concat_gen_end_map(void *ctx)
{
    auto cc = static_cast<concat_context *>(ctx);

    cc->cc_depth -= 1;
    return yajl_gen_map_close(cc->cc_gen_handle) == yajl_gen_status_ok;
}

static int concat_gen_map_key(void *ctx, const unsigned char *key, size_t len)
{
    auto cc = static_cast<concat_context *>(ctx);

    return yajl_gen_string(cc->cc_gen_handle, key, len) == yajl_gen_status_ok;
}

static int concat_gen_start_array(void *ctx)
{
    auto cc = static_cast<concat_context *>(ctx);

    cc->cc_depth += 1;
    if (cc->cc_depth == 1) {
        return 1;
    }
    return yajl_gen_array_open(cc->cc_gen_handle) == yajl_gen_status_ok;
}

static int concat_gen_end_array(void *ctx)
{
    auto cc = static_cast<concat_context *>(ctx);

    cc->cc_depth -= 1;
    if (cc->cc_depth == 0) {
        return 1;
    }
    return yajl_gen_array_close(cc->cc_gen_handle) == yajl_gen_status_ok;
}

static void concat_gen_elements(yajl_gen gen, const unsigned char *text, size_t len)
{
    auto_mem<yajl_handle_t> handle(yajl_free);
    yajl_callbacks callbacks = {nullptr};
    concat_context cc{gen};

    callbacks.yajl_null = concat_gen_null;
    callbacks.yajl_boolean = concat_gen_boolean;
    callbacks.yajl_number = concat_gen_number;
    callbacks.yajl_string = concat_gen_string;
    callbacks.yajl_start_map = concat_gen_start_map;
    callbacks.yajl_end_map = concat_gen_end_map;
    callbacks.yajl_map_key = concat_gen_map_key;
    callbacks.yajl_start_array = concat_gen_start_array;
    callbacks.yajl_end_array = concat_gen_end_array;

    handle = yajl_alloc(&callbacks, nullptr, &cc);
    yajl_config(handle, yajl_allow_comments, 1);
    if (yajl_parse(handle, (const unsigned char *) text, len) != yajl_status_ok ||
        yajl_complete_parse(handle) != yajl_status_ok) {
        unique_ptr<unsigned char, decltype(&free)> err_msg(
            yajl_get_error(handle, 1, (const unsigned char *) text, len), free);

        throw sqlite_func_error("Invalid JSON: {}", (const char *) err_msg.get());
    }
}

static json_string json_concat(nonstd::optional<const char *> json_in, const vector<sqlite3_value *> &values)
{
    yajlpp_gen gen;

    yajl_gen_config(gen, yajl_gen_beautify, false);

    {
        yajlpp_array array(gen);

        if (json_in) {
            concat_gen_elements(gen,
                                (const unsigned char *) json_in.value(),
                                strlen(json_in.value()));
        }

        for (const auto val: values) {
            switch (sqlite3_value_type(val)) {
                case SQLITE_NULL:
                    array.gen();
                    break;
                case SQLITE_INTEGER:
                    array.gen(sqlite3_value_int64(val));
                    break;
                case SQLITE_FLOAT:
                    array.gen(sqlite3_value_double(val));
                    break;
                case SQLITE3_TEXT: {
                    auto text_val = sqlite3_value_text(val);

                    if (sqlite3_value_subtype(val) == JSON_SUBTYPE) {
                        concat_gen_elements(gen,
                                            text_val,
                                            strlen((const char *) text_val));
                    } else {
                        array.gen((const char *) text_val);
                    }
                    break;
                }
            }
        }
    }

    return json_string(gen);
}

struct json_agg_context {
    yajl_gen_t *jac_yajl_gen;
};

static void sql_json_group_object_step(sqlite3_context *context,
                                       int argc,
                                       sqlite3_value **argv)
{
    if ((argc % 2) == 1) {
        sqlite3_result_error(
                context,
                "Uneven number of arguments to json_group_object(), "
                        "expecting key and value pairs",
                -1);
        return;
    }

    json_agg_context *jac = (json_agg_context *) sqlite3_aggregate_context(
            context, sizeof(json_agg_context));


    if (jac->jac_yajl_gen == NULL) {
        jac->jac_yajl_gen = yajl_gen_alloc(NULL);
        yajl_gen_config(jac->jac_yajl_gen, yajl_gen_beautify, false);

        yajl_gen_map_open(jac->jac_yajl_gen);
    }

    for (int lpc = 0; (lpc + 1) < argc; lpc += 2) {
        if (sqlite3_value_type(argv[lpc]) == SQLITE_NULL) {
            continue;
        }

        const unsigned char *key = sqlite3_value_text(argv[lpc]);

        yajl_gen_string(jac->jac_yajl_gen, key, strlen((const char *) key));

        switch (sqlite3_value_type(argv[lpc + 1])) {
            case SQLITE_NULL:
                yajl_gen_null(jac->jac_yajl_gen);
                break;
            case SQLITE3_TEXT: {
                const unsigned char *value = sqlite3_value_text(argv[lpc + 1]);
#ifdef HAVE_SQLITE3_VALUE_SUBTYPE
                int subtype = sqlite3_value_subtype(argv[lpc + 1]);

                if (subtype == JSON_SUBTYPE) {
                    yajl_gen_number(jac->jac_yajl_gen,
                                    (const char *) value,
                                    strlen((const char *)value));
                }
                else {
#endif
                    yajl_gen_string(jac->jac_yajl_gen,
                                    value,
                                    strlen((const char *) value));
#ifdef HAVE_SQLITE3_VALUE_SUBTYPE
                }
#endif
                break;
            }
            case SQLITE_INTEGER: {
                const unsigned char *value = sqlite3_value_text(argv[lpc + 1]);

                yajl_gen_number(jac->jac_yajl_gen,
                                (const char *) value,
                                strlen((const char *) value));
                break;
            }
            case SQLITE_FLOAT: {
                double value = sqlite3_value_double(argv[lpc + 1]);

                yajl_gen_double(jac->jac_yajl_gen, value);
                break;
            }
        }
    }

}

static void sql_json_group_object_final(sqlite3_context *context)
{
    json_agg_context *jac = (json_agg_context *) sqlite3_aggregate_context(
            context, 0);

    if (jac == NULL) {
        sqlite3_result_text(context, "{}", -1, SQLITE_STATIC);
    }
    else {
        const unsigned char *buf;
        size_t len;

        yajl_gen_map_close(jac->jac_yajl_gen);
        yajl_gen_get_buf(jac->jac_yajl_gen, &buf, &len);
        sqlite3_result_text(context, (const char *) buf, len, SQLITE_TRANSIENT);
#ifdef HAVE_SQLITE3_VALUE_SUBTYPE
        sqlite3_result_subtype(context, JSON_SUBTYPE);
#endif
        yajl_gen_free(jac->jac_yajl_gen);
    }
}

static void sql_json_group_array_step(sqlite3_context *context,
                                      int argc,
                                      sqlite3_value **argv)
{
    json_agg_context *jac = (json_agg_context *) sqlite3_aggregate_context(
            context, sizeof(json_agg_context));

    if (jac->jac_yajl_gen == NULL) {
        jac->jac_yajl_gen = yajl_gen_alloc(NULL);
        yajl_gen_config(jac->jac_yajl_gen, yajl_gen_beautify, false);

        yajl_gen_array_open(jac->jac_yajl_gen);
    }

    for (int lpc = 0; lpc < argc; lpc++) {
        switch (sqlite3_value_type(argv[lpc])) {
            case SQLITE_NULL:
                yajl_gen_null(jac->jac_yajl_gen);
                break;
            case SQLITE3_TEXT: {
                const unsigned char *value = sqlite3_value_text(argv[lpc]);
#ifdef HAVE_SQLITE3_VALUE_SUBTYPE
                int subtype = sqlite3_value_subtype(argv[lpc]);

                if (subtype == JSON_SUBTYPE) {
                    yajl_gen_number(jac->jac_yajl_gen,
                                    (const char *) value,
                                    strlen((const char *)value));
                }
                else {
#endif
                    yajl_gen_string(jac->jac_yajl_gen,
                                    value,
                                    strlen((const char *) value));
#ifdef HAVE_SQLITE3_VALUE_SUBTYPE
                }
#endif
                break;
            }
            case SQLITE_INTEGER: {
                const unsigned char *value = sqlite3_value_text(argv[lpc]);

                yajl_gen_number(jac->jac_yajl_gen,
                                (const char *) value,
                                strlen((const char *) value));
                break;
            }
            case SQLITE_FLOAT: {
                double value = sqlite3_value_double(argv[lpc]);

                yajl_gen_double(jac->jac_yajl_gen, value);
                break;
            }
        }
    }

}

static void sql_json_group_array_final(sqlite3_context *context)
{
    json_agg_context *jac = (json_agg_context *) sqlite3_aggregate_context(
            context, 0);

    if (jac == NULL) {
        sqlite3_result_text(context, "{}", -1, SQLITE_STATIC);
    }
    else {
        const unsigned char *buf;
        size_t len;

        yajl_gen_array_close(jac->jac_yajl_gen);
        yajl_gen_get_buf(jac->jac_yajl_gen, &buf, &len);
        sqlite3_result_text(context, (const char *) buf, len, SQLITE_TRANSIENT);
#ifdef HAVE_SQLITE3_VALUE_SUBTYPE
        sqlite3_result_subtype(context, JSON_SUBTYPE);
#endif
        yajl_gen_free(jac->jac_yajl_gen);
    }
}

int json_extension_functions(struct FuncDef **basic_funcs,
                             struct FuncDefAgg **agg_funcs)
{
    static struct FuncDef json_funcs[] = {
        sqlite_func_adapter<decltype(&json_concat), json_concat>::builder(
            help_text("json_concat",
                      "Returns an array with the given values concatenated onto the end.  "
                      "If the initial value is null, the result will be an array with "
                      "the given elements.  If the initial value is an array, the result "
                      "will be an array with the given values at the end.  If the initial "
                      "value is not null or an array, the result will be an array with "
                      "two elements: the initial value and the given value.")
                .sql_function()
                .with_parameter({"json", "The initial JSON value."})
                .with_parameter(help_text("value", "The value(s) to add to the end of the array.")
                                    .one_or_more())
                .with_tags({"json"})
                .with_example({
                    "To append the number 4 to null",
                    "SELECT json_concat(NULL, 4)"
                })
                .with_example({
                    "To append 4 and 5 to the array [1, 2, 3]",
                    "SELECT json_concat('[1, 2, 3]', 4, 5)"
                })
                .with_example({
                    "To concatenate two arrays together",
                    "SELECT json_concat('[1, 2, 3]', json('[4, 5]'))"
                })
        ),

        sqlite_func_adapter<decltype(&json_contains), json_contains>::builder(
            help_text("json_contains", "Check if a JSON value contains the given element.")
                .sql_function()
                .with_parameter({"json", "The JSON value to query."})
                .with_parameter({"value", "The value to look for in the first argument"})
                .with_tags({"json"})
                .with_example({
                    "To test if a JSON array contains the number 4",
                    "SELECT json_contains('[1, 2, 3]', 4)"
                })
                .with_example({
                    "To test if a JSON array contains the string 'def'",
                    "SELECT json_contains('[\"abc\", \"def\"]', 'def')"
                })
        ),

        {
            "jget", -1, SQLITE_UTF8, 0, sql_jget,
            help_text("jget",
                      "Get the value from a JSON object using a JSON-Pointer.")
                .sql_function()
                .with_parameter({"json", "The JSON object to query."})
                .with_parameter({"ptr", "The JSON-Pointer to lookup in the object."})
                .with_parameter(help_text("default", "The default value if the value was not found")
                                    .optional())
                .with_tags({"json"})
                .with_example({
                    "To get the root of a JSON value",
                    "SELECT jget('1', '')"
                })
                .with_example({
                    "To get the property named 'b' in a JSON object",
                    "SELECT jget('{ \"a\": 1, \"b\": 2 }', '/b')"
                })
                .with_example({
                    "To get the 'msg' property and return a default if it does not exist",
                    "SELECT jget(null, '/msg', 'Hello')"
                })
        },

        { nullptr }
    };

    static struct FuncDefAgg json_agg_funcs[] = {
            { "json_group_object", -1, 0,
                    sql_json_group_object_step, sql_json_group_object_final,
                    help_text("json_group_object")
                        .sql_function()
                        .with_summary("Collect the given values from a query into a JSON object")
                        .with_parameter(help_text("name", "The property name for the value"))
                        .with_parameter(help_text("value", "The value to add to the object")
                                            .one_or_more())
                        .with_tags({"json"})
                        .with_example({
                            "To create an object from arguments",
                            "SELECT json_group_object('a', 1, 'b', 2)"
                        })
                        .with_example({
                            "To create an object from a pair of columns",
                            "SELECT json_group_object(column1, column2) FROM (VALUES ('a', 1), ('b', 2))"
                        })},
            { "json_group_array", -1, 0,
                    sql_json_group_array_step, sql_json_group_array_final,
                    help_text("json_group_array")
                        .sql_function()
                        .with_summary("Collect the given values from a query into a JSON array")
                        .with_parameter(help_text("value", "The values to append to the array")
                                            .one_or_more())
                        .with_tags({"json"})
                        .with_example({
                            "To create an array from arguments",
                            "SELECT json_group_array('one', 2, 3.4)"
                        })
                        .with_example({
                            "To create an array from a column of values",
                            "SELECT json_group_array(column1) FROM (VALUES (1), (2), (3))"
                        })},

            { nullptr }
    };

    *basic_funcs = json_funcs;
    *agg_funcs   = json_agg_funcs;

    return SQLITE_OK;
}
